Screw-down crowns are commonly used to equip watches in order to improve the sealing of said watches at their winding or control stem. This type of crown has the peculiarity of being able to assume an unscrewed position in which the watch can be wound, set etc., and a screwed-down position in which the crown is screwed down and locked onto a tube pressed or screwed into the middle part of the watch case to compress a sealing gasket, thereby improving the sealing of the watch. The screwed-down position in thus that which corresponds to the normal position when the watch is worn and which is more or less always the same, with the exception of wear to the sealing gasket.
The manufacture and assembly of these screw-down crowns in watch cases are well known. However, the methods for assembling such crowns are ill suited to screw-down crowns bearing an inscription or a motif, for example a logo, a trademark or similar sign, on their end face. Indeed, known manufacturing methods do not generally allow the crown to be brought into a determined orientation with respect to the case once screwed down, which impairs the aesthetic appearance of the case when an inscription is applied to the end face of the crown. This situation is, of course, unacceptable when such crowns are fitted to high quality and luxury products.
One solution that allows a crown to be adjusted in a determined position or orientation after being screwed onto the tube has already been proposed in EP Patent Application 1124167A1. According to this document, a ring made of shape memory alloy is placed either between the case middle and the tube, or between the crown and the tube. By using the deformation of the ring, in particular reducing its diameter by subjecting the watch to specific temperatures, a temporary clearance can be created between the case middle and the tube and between the crown and the tube respectively, and this clearance allows angular adjustment of the crown in its screwed-down position. A drawback of this solution lies in the fact that shape memory alloys are not currently available in the form of bars of small dimensions, so that it is difficult and expensive to machine the rings in question in the small dimensions required for the applications concerned. Moreover, this process is only intended for the initial assembly of the crown by the watch manufacturer, but not for subsequent operations to adjust the orientation of the crown, which would risk damaging other parts of the watch which are sensitive to temperature variations.
EP Patent 1701225 describes a screw-down orientable crown including a head integral with a winding stem and a cover on which an inscription appears, the head and the cover being integral in rotation by means of truncated cone-shaped surfaces held in contact with one another via a resilient element. Adjustment of the angular position of the cover is achieved by axially pulling out the latter relative to the case middle along the longitudinal axis of the crown. A major drawback of this solution is that the cover is made integral in rotation with respect to the head only by the friction forces between the truncated cone-shaped surfaces, which is not sufficiently reliable over the service life of a watch, and particularly when the compression forces exerted by the resilient element gradually diminish. Moreover, another drawback is that it is not possible to guarantee that the same angular position can be obtained in a precise manner, since the angular position can only be determined by successive approximations.
EP Patent 1411401 describes a crown comprising an orientable substrate on its upper outer face, the substrate being provided with an inscription and rotationally disengageable from the head of the crown when pressure is exerted against braking means. The drawback of this solution is that it is not robust to shocks, which may also exert a pressure force on the substrate and thereby reorientate the substrate in an undesired manner with respect to the body of the crown. Moreover, numerous precautions must be taken when handling the crown to avoid applying any pressure force towards the case middle to prevent an untimely rotation of the substrate, which makes the crown inconvenient to use.